Sensor for use with a drug delivery device

ABSTRACT

An optical decoding system including an optical sensor integral with or attachable to a housing of a drug delivery device and configured to be directed at first and second rotatable components of a dose setting and dispensing mechanism of the drug delivery device and a processor configured to: (i) cause the optical sensor to capture images of the first and second rotatable components at least at the beginning and end of a medicament dose dispensing process; (ii) determine a rotational position of both the first and second rotatable components in each of the captured images; and (iii) determine from the rotational positions of the first and second rotatable components an amount of medicament delivered by the dose setting and dispensing mechanism of the drug delivery device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/543,507, filed on Jul. 13, 2017, which is a U.S. national stageapplication under 35 USC § 371 of International Application No.PCT/EP2016/050665, filed on Jan. 14, 2016, which claims priority toEuropean Patent Application No. 15151370.2, filed on Jan. 16, 2015, theentire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The disclosure relates to a sensor assembly which is integrated with oralternatively removably attachable to a drug delivery device such as aninjection pen.

BACKGROUND

A variety of diseases exists that require regular treatment by injectionof a medicament. Such injection can be performed by using injectiondevices, which are applied either by medical personnel or by patientsthemselves. As an example, type-1 and type-2 diabetes can be treated bypatients themselves by injection of insulin doses, for example once orseveral times per day. For instance, a pre-filled disposable insulin pencan be used as an injection device. Alternatively, a re-usable pen maybe used. A re-usable pen allows replacement of an empty medicamentcartridge by a new one. Either pen may come with a set of one-wayneedles that are replaced before each use. The insulin dose to beinjected can then for instance be manually selected at the insulin penby turning (dialing) a dosage knob and observing the actual dose from adose window or display of the insulin pen. The dose is then injected byinserting the needle into a suited skin portion and pressing aninjection button of the insulin pen. To be able to monitor insulininjection, for instance to prevent false handling of the insulin pen orto keep track of the doses already applied, it is desirable to measureinformation related to a condition and/or use of the injection device,such as for instance information on the injected insulin type and dose.

It has been described, for instance in WO 2011/117212, to provide asupplementary device comprising a mating unit for releasably attachingthe device to an injection/drug delivery device. The device includes acamera and is configured to perform optical character recognition (OCR)on captured images visible through a dosage window of the injection pen,thereby to determine a dose of medicament that has been dialed into theinjection device.

SUMMARY

A first aspect of the disclosure provides an optical decoding systemcomprising: an optical sensor integral with or attachable to a housingof a drug delivery device and configured to be directed at first andsecond rotatable components of a dose setting and dispensing mechanismof the drug delivery device; and a processor configured to: cause theoptical sensor to capture images of the first and second rotatablecomponents at least at the beginning and end of a medicament dosedispensing process; determine a rotational position of both the firstand second rotatable components in each of the captured images; anddetermine from the rotational positions of the first and secondrotatable components an amount of medicament delivered by the dosesetting and dispensing mechanism of the drug delivery device.

The processor may be further configured to cause the optical sensor tocapture images of the first and second rotatable components during amedicament dose setting process. The processor may be further configuredto determine from the captured images whether the drug delivery deviceis in a medicament dose dialing mode or a medicament dose dispensingmode. In the medicament dose dialing mode, the first rotatable componentmay rotate in a first direction and the second rotatable component mayremain stationary and in the medicament dose dispensing mode the firstrotatable component may rotate in a second direction opposite to thefirst direction and the second rotatable component may rotate in thefirst direction.

The processor may be further configured to identify encoded imagesassociated with each of the first and second rotatable components, eachencoded image encoding a different rotational orientation of therespective rotatable component.

The lowest common multiple of the number of unique rotationalorientations of the first and second rotatable components may be higherthan a maximum dose which can be dialed into the drug delivery device.The maximum dose which can be dialed into the drug delivery device maybe 120 units.

The processor may be configured to determine the rotational orientationof both the first and second rotatable components at the beginning andend of the medicament dose dispensing process and to use the determinedorientations to determine the amount of medicament dispensed.

The first rotatable component may be a hollow cylindrical number sleevehaving numbers marked on a first portion of an outer surface. Theencoded images may be provided on a second potion of the outer surface.The second rotatable component may be a gear wheel having a plurality ofteeth. The encoded images on the gear wheel may be marked on the crestsof each gear tooth.

The optical sensor may be configured to be activated by movement of thefirst rotatable component. The optical decoding system may furthercomprise a switch. A change in the state of the switch may be configuredto cause the optical sensor to be activated.

The drug delivery device and switch may be configured to be arrangedsuch that the state of the switch changes when the drug delivery devicemoves from a zero unit drug dose arrangement to a single unit drug dosearrangement.

The optical decoding system may further comprise a display device. Theprocessor may be configured to cause the display device to display anindication of the amount of medicament that has been delivered.

The optical decoding system may further comprise one or more LEDsconfigured to illuminate portions of the first and/or second rotatablecomponents.

The optical decoding system may be part of a supplementary deviceconfigured to be attached to the drug delivery device.

A second aspect of the disclosure provides a medicament delivery systemcomprising:

a drug delivery device comprising first and second rotatable componentseach having a plurality of encoded images disposed around an outersurface thereof, and wherein each of the encoded images corresponds to adiscreet rotational orientation of the respective component; and anoptical decoding system according to any preceding claim retained in ahousing of the drug delivery device.

In the medicament delivery system: the first rotatable component may bea hollow cylindrical number sleeve having numbers marked on a firstportion of an outer surface; the encoded images on the number sleeve maybe provided on a second potion of the outer surface; the secondrotatable component may be a gear wheel having a plurality of teeth; andthe gear wheel may be engaged with a drive sleeve of the drug deliverydevice during the medicament dose dispensing process.

The number of encoded images on the number sleeve may be 24 and numberof encoded images on the gear wheel may be 7.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of example embodiments of the presentdisclosure, reference is now made to the following description taken inconnection with the following Figures, in which:

FIG. 1 shows two views of a drug delivery device 1 with which a sensordevice according to various embodiments of the disclosure may be used;

FIGS. 2A to 2E are illustrative simplified views of various components,and combinations of components, of a drug delivery device such as thatof FIG. 1 with which a sensor device according to various embodimentsmay be used;

FIGS. 3A to 3C are illustrative simplified views of various componentsof a drug delivery device with which sensor devices according to variousembodiments of the disclosure may be used;

FIG. 4 is a cross-section showing a drug dose setting and dispensingmechanism of a drug delivery device;

FIG. 5A is a cross-section showing some components of a drug dosesetting and dispensing mechanism of a drug delivery device for use inthe present disclosure and a schematic illustration of an optical sensorarrangement according to embodiments of the disclosure;

FIG. 5B is a perspective view showing some components of a drug dosesetting and dispensing mechanism of a drug delivery device for use inthe present disclosure;

FIG. 6 is simplified block diagram of a sensor device according toembodiments of the disclosure; and

FIG. 7 is a table illustrating the rotational orientations of therotatable components of the drug delivery device at different medicamentdoses.

DETAILED DESCRIPTION

The drug delivery device 1 of FIG. 1 is configured such that a user isable to adjust the drug dosage (or number of drug doses) that is to bedelivered (or dispensed) using the device 1. In the example of FIG. 1,this is achieved by rotating (or dialing) a dose selector 10 whichcauses an internal dialing mechanism (not shown) to adjust an amount ofthe drug that is to be dispensed once a drug delivery mechanism (notshown) is actuated. In this example, the drug delivery mechanism isactuated by pressing a button 11 on the device.

The drug delivery device 1 comprises an external housing 12 in which isformed at least one aperture or window 13A, 13B. As will be appreciated,an aperture may simply be a cut-away area of the external housing 12,whereas a window may be a transparent portion of the housing throughwhich components of the device may be seen. For convenience, the atleast one aperture or window 13A, 13B, will hereafter simply be referredto as the at least one window.

The at least one window 13A, 13B allows a movable gauge element 14 to bevisible from the exterior of the housing 12. The drug delivery device isconfigured such that as the dose selector 10 is dialed, the movablegauge element 14 is caused to be moved thereby to indicate a selecteddose to the user. More specifically, as the dose selector 10 is dialed,the gauge element 14 moves axially along an underlying surface 15A, 15Bthereby to indicate the selected dose. In the example of FIG. 1, asurface 15A underlying at least part of the gauge element 14 comprises anumber sleeve 15A. The number sleeve 15A has numbers indicative of drugdoses provided on its outer surface, with the number indicating thecurrently selected dose being visible through the at least one window13A, 13B. In this example, the number sleeve 15A is visible through agauge window (or aperture) 14-1 formed in the movable gauge element.Other parts of the movable gauge element 14 are discussed below.

The uppermost view of the drug delivery device 1 shown in FIG. 1illustrates the situation before any dialing has been performed.Consequently, the movable gauge element 14 is at its first (or initial)position at a first end of the path along which it is able to move. Inthis example, when the movable gauge element 14 is at the first end ofits path, the portion of the number sleeve 15A that is visible throughthe gauge window 14-1 shows the number zero (i.e. a zero dose).

The bottommost view of the drug delivery device 1 shown in FIG. 1illustrates the situation after dialing has been performed.Consequently, the movable gauge element 14 has moved axially along thepath that is visible through the first window 13A away from its firstposition. In this example, the device 1 has been dialed to its maximumdose and as such, the movable gauge element 14 has moved to the secondend of its path. The maximum dose in this example is “100” and so theportion of the number sleeve 15A that is visible through the gaugewindow 14-1 shows the number “100”. In some other embodiments, themaximum dose is “120”, however the amount of medicament or individualdoses able to be dialed into the device is not essential.

In this example, the device 1 comprises first and second windows 13A,13B. The number sleeve 15A underlies and is visible through the firstwindow 13A, whereas a further underlying element 15B underlies and issometimes visible through the second window 13B. The further underlyingelement 15B may or may not include any numbers. The further underlyingsurface 15B is visually distinguishable from a second part 14-2 of themovable gauge element 14 which overlies it and which is configured tomove axially along it. For instance, the second part 14-2 of the movablegauge element 14 may be of a different reflectance to the furtherunderlying surface 15B. For example, one of the gauge element 14 and theunderlying surface 15B may be of a light color (e.g. may be made of alight colored polymer) and the other may be of dark color (e.g. may bemade of a dark colored polymer). The user may, therefore, be able todetermine the selected dose by determining the proportion of the secondwindow 13A in which the gauge element 14 (specifically, the second part14-2) is visible compared to the proportion in which the furtherunderlying surface 15B is visible. This can be seen from FIG. 1, inwhich, when the device 1 is dialed to its zero dose, the gauge element14 covers the entire length of the path that is visible through thesecond window 13B. In contrast, when the device 1 is dialed to itsmaximum dose, none of the gauge element 14 is visible through the secondwindow. Instead, the further underlying surface 15B is visible along theentire length of the path defined by the second window 13B.

The number sleeve 15A (which is also the surface underlying the gaugeelement 14) is also visually distinguishable from the movable gaugeelement 14 which overlies it and which is configured to move axiallyalong it. For instance, gauge element 14 may be of a differentreflectance to the number sleeve 15A. For example, one of the gaugeelement 14 and the underlying surface 15A may be of a light color (e.g.may be made of a light colored polymer) and the other may be of darkcolor (e.g. may be made of a dark colored polymer). In the examplesshown in the Figures, the number sleeve 15A and underlying surface 15Bare of a higher reflectance than the movable gauge element 14.

FIGS. 2A to 2E are simplified schematics of components of a drugdelivery device such as that of FIG. 1. The purpose of FIGS. 2A to 2E isto illustrate the operation of a drug delivery device 1 such as that ofFIG. 1; they are not intended to be accurate representations of theexact design of the components.

FIG. 2A is a simplified schematic of the number sleeve 15A. The sleeve15A has numbers provided on its surface. In some examples, the numbers,ranging from the minimum dose to the maximum dose, may be providedhelically around the surface of the number sleeve.

FIG. 2B is a simplified schematic of a movable gauge element 14. Thegauge element 14 comprises a first section 14-4 in which the gaugewindow 14-1 is provided. In this example, the first section is 14-1 acollar which is configured to encircle the number sleeve 15A (as can beseen in FIGS. 2C and 2D). Extending in opposite directions from thefirst section 14-4 are the second part 14-2 and a third part 14-2. Thesecond and third parts 14-2, 14-3 extend generally parallel to thelongitudinal axis of the number sleeve.

The second part 14-2 of the movable gauge element is configured toextend from the first part 14-2 by a length sufficient to fill theentire second window 13B when the movable gauge is in its firstposition. The second part 14-2 may also serve to obscure a portion ofthe exterior surface of the number sleeve 15A, when the gauge elementmoves away from its first position. The third part of the movable gaugeelement 15-3 is configured to obscure a portion of the exterior surfaceof the number sleeve 15A, when the gauge elements moves between itsfirst and second positions. In this way, only the portion of the numbersleeve that underlies the gauge window 14-1 is visible through the firstwindow 13A of the device housing 12.

The number sleeve 15A is rotatable about its longitudinal axis withinthe device housing 12. As such, the number sleeve 15A may be referred toas a movable (or rotatable) component. Rotation of the number sleeve 15Ais in some embodiments caused by rotation of the dose selector 10.

The rotational movement NS_(R) of the number sleeve 15A and axialmovement G_(E) of the gauge element 14 are interdependent. Put anotherway, the dialing mechanism of the device 1 is configured such that whennumber sleeve 15A is caused to rotate, the gauge element 14 is caused tomove or translate axially along its path. Moreover, the degree ofrotation of the number sleeve 15A corresponds proportionally to theextent of axial movement of the gauge element 14.

FIG. 2C shows the gauge element 14 in its initial position in which, inthis example, it indicates a zero dose. FIG. 2D shows the number sleeve15A and gauge element 14 following rotation of the number sleeve 15A andtranslation of the gauge element 14 from its first position. FIG. 2Eshows this arrangement of FIG. 2D within a simplified version of thedevice housing 12.

FIG. 3A shows an example of a rotatable component 65A, in this instancea number sleeve 65A, which may form part of a drug delivery device 6 foruse with sensor devices 2 according to embodiments of the disclosure.FIGS. 3B and 3C show two different simplified views of a delivery device6 including the rotatable element 65A of FIG. 3A. The delivery device ofFIGS. 3A-C may be generally the same as that described with reference tothe previous figures except for the differences described below.

As with the previously described delivery device 1, the rotation of therotatable component 65A is interdependent with the axial movement of themovable gauge element 14. The degree of rotation may be proportional tothe axial movement of the movable gauge element 14. In the examples ofFIG. 3A, the rotatable element 65A has, provided around its exteriorsurface, a visually-distinguishable code 66 for allowing its rotationalorientation to be determined. For example, the mechanism of the deliverydevice 1 may be arranged so that one full rotation of the number sleeve15A corresponds to 24 dialed units of medicament. Thus the number sleeve15A may be rotatable into any one of 24 unique rotational orientations.For each of these rotational positions a different code may be provided.The code 66 may take any suitable form so long as it allows therotational orientation of rotatable element to be determined by thesensor device 2. In this example, the code 66 is provided at an end ofthe number sleeve 65A.

The housing 12 of the drug delivery device 6 includes a further apertureor window 63 through which a portion of the rotatable element 65A, onwhich part of the code 66 is provided, is visible. The further window 63is positioned and oriented relative to the rotatable element 65A suchthat a portion of the code is externally visible through the furtherwindow 63 regardless of the rotational orientation of the rotatableelement 65A. The further window 63 is positioned and oriented relativeto the rotatable element 65A such that, as the rotatable element rotatesthrough a single complete rotation, a different section of the code 66is visible at each rotational orientation. The further aperture is, inthis example, provided on a different side of the device housing 12 (or,if the housing is cylindrical or otherwise rounded, around the exteriorsurface of the device housing 12) from the at least one window 13A, 13Bthrough which the movable gauge element 14 is visible. In this way, themovable gauge element 14 does not obstruct the code from view.

FIG. 4 shows a cross-sectional view of a medicament setting and deliverymechanism of a drug delivery device 1. The further window 63 is notshown in FIG. 4. As previously described, the drug delivery device 1 hastwo modes of operation, a medicament dose dialing mode and a medicamentdose delivery (or dispensing) mode. The medicament setting and deliverymechanism comprises a drive sleeve 72, which is a hollow cylindricalcomponent. The drive sleeve 72 is arranged so that it does not rotateduring dialing. A torsion spring 78 is provided which is secured at oneend to the body of the drug delivery device 1 and at the other end tothe number sleeve 15A. The torsion spring 78 biases the number sleeve15A towards the zero dose position. When the number sleeve 15A isrotated to dial in a dose, the tension in the torsion spring 78 isfurther increased. The drive sleeve 72 may have a splined interface withan inner part of the body of the drug delivery device 1 which preventsrelative rotation during dose dialing. The drive sleeve 72 is also incontact with a clutch member 76 connected to the button 11. When thedelivery button 11 is depressed the drive sleeve 72 is therefore movedlongitudinally. This moves the splines on the drive sleeve 72 out ofengagement with the splines on the body so that the drive sleeve is freeto rotate. Further splines on the drive sleeve 72 engage withcorresponding splines on the number sleeve 15A when the button 11 isdepressed so that rotation of the number sleeve 15A under action of thetorsion spring also causes rotation of the drive sleeve 72.

A lead screw 80 is provided in the body of the drug delivery device 1.Axial advancement of the lead screw 80 causes medicament to be expelledfrom the medicament cartridge. The lead screw 80 is rotationally lockedrelative to the drive sleeve 72 via a splined interface and has athreaded connection to the body of the drug delivery device 1.Therefore, when the drive sleeve 72 rotates during a medicamentdispensing process, the lead screw 80 also rotates and is forced toadvance axially by the threaded connection to the body.

In embodiments of the disclosure, the drug delivery device 1 comprisesan additional gear wheel 70 which is not shown in FIG. 4, but is visiblein FIG. 5A. The gear wheel 70 is rotatably mounted in the housing and isvisible through the further window 63. The gear wheel 70 may be mountedon a pin, or may have an integrally molded axle which is retained in arecess provided in the housing. In some embodiments, the gear wheel is atoothed gear which can engage with corresponding teeth provided on thecartridge end of the drive sleeve 72.

The drive sleeve 72 is visible in cross-section in FIG. 5A. The end ofthe drive sleeve 72 showing the teeth on the outer surface is visible inperspective in FIG. 5B. The medicament cartridge holder 74 is alsovisible in FIG. 5B.

The drug delivery device may include an optical sensor arrangement 2,shown schematically in FIG. 5A. The optical sensor arrangement 2 may insome embodiments be part of a supplemental device designed to bereleasably attachable to the drug delivery device 1. In some otherembodiments, the optical sensor arrangement 2 is an integral part of thedrug delivery device 1. The optical sensor arrangement 2 is arranged andhas a field of view such that it can capture images of the gear wheel 70and portion of the number sleeve 15A containing thevisually-distinguishable code 66. The optical sensor arrangement 2 maycapture a single image in which both of these components are visible, ormay capture images of each component separately in quick succession.

The gear wheel 70 has a number of encoded images marked on its outsurface such that they are visible in images captured by the opticalsensor arrangement 2. Each of these encoded images may uniquely encode arotational position (or orientation) of the gear wheel 70. As such, theimages may be printed or otherwise marked on the crests of the teeth orin the troughs between the teeth. The encoded images may take anysuitable form, for example each may be a bar code or dot matrix.

FIG. 6 shows a simplified schematic block diagram of an optical sensorarrangement 2 according to various embodiments. The optical sensorarrangement 2 comprises an optical sensor 20, which may comprise anarray of light sensitive elements. These are configured to outputsignals to circuitry 21. The circuitry 21 may be of any suitablecomposition and may comprise any combination of one or more processorsand/or microprocessors 210 (for simplicity, hereafter referred to as“the at least one processor”) suitable for causing the functionalitydescribed herein to be performed. The circuitry 21 may additionally oralternatively comprise any combination of one or more hardware-onlycomponents such as ASICs, FPGAs etc. (which are not shown in FIG. 6).

The circuitry 21 may further comprise any combination of one or morenon-transitory computer readable memory media 211, such as one or bothof ROM and RAM, which is coupled to the at least one processor 210. Thememory 211 may have computer-readable instructions 211A stored thereon.The computer readable instructions 211A, when executed by the at leastone processor 210 may cause the optical sensor arrangement 2 to performthe functionality described in this specification, such as controllingoperation of the sensor 20 and interpreting the signals receivedtherefrom.

The optical sensor arrangement 2 comprises at least one light source 23.The light source 23 is for illuminating the encoded information 66 onthe number sleeve 15A and the encoded images on the gear wheel 70. Thesensor 20 is configured read the encoded information by capturing animage. The image is captured by detecting the light reflected back fromdifferent parts of the surface(s) on which the image is provided. Thecaptured images are then passed to the circuitry 21 for interpretation.

The optical sensor arrangement 2 may further comprise one or both of adisplay screen 24 (such as an LED or LCD screen) and a data port 25. Thedisplay screen 24 may be operable under the control of the circuitry 21to display information regarding operation of the drug delivery device 1to the user. For instance, the information determined by the opticalsensor arrangement 2 may be displayed to the user. The informationdetermined by the optical sensor arrangement 2 may include the currentmode of operation of the device 1 and the delivered medicament dose.

The data port 25 may be used to transfer stored information relating tothe operation of the drug delivery device 1 from the memory 211 to aremote device such a PC, tablet computer, or smartphone. Similarly, newsoftware/firmware may be transferred to the sensor device via the dataport 25. The data port 25 may be a physical port such as a USB port ormay be a virtual, or wireless, port such as an IR, WiFi or Bluetoothtransceiver. The optical sensor arrangement 2 may further comprise aremovable or permanent (preferably rechargeable with e.g. photovoltaiccells) battery 26 for powering the other components of the device 2.Instead of the battery 26, a photovoltaic or capacitor power source maybe used.

The optical sensor arrangement 2 may be configured to capture numerousimages of the number sleeve 15A and gear wheel 70 and to determine fromthese whether the drug delivery device 1 is in a dialing mode or adelivery mode and if the device 1 is in a delivery mode, what dose ofmedicament has been delivered. As previously described, the gear wheel70 has teeth which engage corresponding teeth on the drive sleeve 72.This engagement may occur at all times, or alternatively only when thedrive sleeve 72 is shifted axially when the button 11 is depressed. Ineither case, as the drive sleeve 72 does not rotate during a dialingprocess, the gear wheel 70 also remains stationary during dialing. Theoptical sensor arrangement 2 may be configured to capture images atregular intervals whenever a dose is being dialed i.e. whenever it isdetected that the number sleeve 15A is rotating. If it can be seen inany two images that the number sleeve 15A has moved, but that gear wheel70 has remaining stationary, then it can be inferred that the device 1is in a medicament dose dialing mode. If it can be seen in any twoimages that both the number sleeve 15A and the gear wheel 70 have moved,then it can be inferred that the device 1 is in a medicament dosedelivery mode. The fact that the number sleeve 15A and gear wheel 70rotate in opposite directions during the dose delivery process may makeit easier for the optical sensor arrangement 2 to determine that onlythe number sleeve 15A is rotating in the dose dialing mode.

In order to determine a dose which has been delivered from the drugdelivery device 1, the optical sensor arrangement 2 compares an imagetaken at the beginning of the dose dispensing process and at the end ofthe dose dispensing process. The position of the gear wheel 70 beforeand after the dispense process is compared with the position of thenumber sleeve 15A at the beginning of the dispense process (the numbersleeve 15A always returns to the same position at the end of thedispense process provided that the whole dialed dose is ejected). Insome embodiments, the number sleeve may occupy one of 24 uniquerotational orientations, however up to 120 units of medicament may bedialed in and delivered from the device 1. The number sleeve 15A maytherefore undergo more than one full revolution. If only the numbersleeve were present, then it would not be possible for the opticalsensor arrangement 2 to determine the absolute position of the numbersleeve 15A. For example, it would not be possible to distinguish betweena dialed dose of 24 units and 48 units, as the number sleeve 15A wouldbe in the same rotational orientation in these cases. It would thereforenot be possible to determine the dispensed dose with certainty.

Thus the gear wheel 70 is provided with a different number of teeth. Inparticular, the lowest common multiple of the number of teeth of thegear wheel and the number of unique rotational positions of the numbersleeve 15A is greater than the maximum dose which can be dialed into thedevice 1. For example, the gear wheel 70 may comprise 7 teeth, thenumber sleeve 15A may have 24 unique positions per revolution and themaximum dialed dose may be 120 units. The lowest common multiple of 7and 24 is 168. In another example, the number sleeve 15A may have only20 unique rotational orientations. The maximum dialable dose may stillbe 120 units or may be reduced, for example to 100 units. In this case agear wheel having 9 teeth, each with a unique encoded image, could beused. In general the number sleeve 15A may have an even number of uniquerotational orientations and the gear wheel 70 may have an odd number ofunique rotational orientations. However, in some embodiments thearrangement may be reversed such that the number sleeve 15A has an oddnumber of unique rotational orientations and the gear wheel 70 has aneven number. Software residing in the optical sensor arrangement 2 isconfigured to isolate the two encoded images visible in each capturedimage, so that the positions of the number sleeve 15A and gear wheel 70are accurately determined.

FIG. 7 is a table illustrating the way in which the optical sensorarrangement 2 can determine with certainty the medicament dose that hasbeen delivered using the start and end orientations of the number sleeve15A and gear wheel 70. For example, if 3 units are dialed in, then boththe number sleeve 15A and gear wheel 70 will display the encoded imageassociated with the third tooth (the third unique rotational orientationfor each component). If 27 units are dialed in, the number sleeve willagain display the encoded image associated with the third tooth, howeverthe gear wheel will display the encoded image associated with the sixthtooth. Thus the gear wheel 70 effectively allows the optical sensorarrangement 2 to determine how many complete rotations the number sleeve15A has performed.

In order to reduce power consumption, the optical sensor arrangement 2may not be powered on at all times, but may instead be “woken” inresponse to movement of the dose setting mechanism. Initial movement ofthe number sleeve 15A when a dialing process begins may trigger the wakeup of the optical sensor arrangement 2. For example, if the opticalsensor arrangement 2 is part of an attachable supplemental device, thesupplemental device may be provided with a mechanical sensing pin whichis caused to move when the number sleeve 15A moves from a zero doseposition to a single unit dose position. If the optical sensorarrangement 2 is integral with the drug delivery device 1, then thesensing pin is internal or may be replaced with a conductive, magnetic,capacitive or optical sensor. The ‘wake-up’ signal may last until thedrug delivery device 1 switches to a drug delivery mode, or until it isdetected that the rotational components have been stationary for apredetermined period of time.

Alternatively, the optical sensor arrangement 2 may be configured tocapture images only during the medicament dose dispensing process, oronly and the beginning and end of the medicament dose dispensingprocess. Thus, the trigger may wake-up the optical sensor arrangement 2when the button 11 is depressed.

The invention claimed is:
 1. An optical decoding system comprising: a single optical sensor integral with or attachable to a housing of a drug delivery device and configured to be directed at first and second movable components of a dose setting and dispensing mechanism of the drug delivery device; and a processor configured to: cause the single optical sensor to capture one or more images of the first and the second movable components at least at a beginning and an end of a medicament dose dispensing process.
 2. The optical decoding system according to claim 1, wherein the processor is configured to determine information relating to operation of the drug delivery device from the one or more images.
 3. The optical decoding system according to claim 2, wherein the processor is configured to determine the information relating to operation of the drug delivery device by comparing the one or more images of the first and second movable components.
 4. The optical decoding system according to claim 1, wherein the processor is configured to cause the single optical sensor to capture the one or more images of the first and second movable components during a medicament dose setting process.
 5. The optical decoding system according to claim 4, wherein the processor is configured to determine based on the one or more images whether the drug delivery device is in a medicament dose dialing mode or a medicament dose dispensing mode.
 6. The optical decoding system according to claim 5, wherein in the medicament dose dialing mode, the first movable component is configured to move in a first direction and the second movable component remains stationary and in the medicament dose dispensing mode the first movable component is configured to move in a second direction opposite to the first direction and the second movable component is configured to move in the first direction.
 7. The optical decoding system according to claim 1, wherein the processor is configured to identify encoded images associated with each of the first and second movable components, each encoded image encoding a different position of the respective movable component.
 8. The optical decoding system according to claim 5, wherein the lowest common multiple of the number of unique positions of the first and second movable components is higher than a maximum dose which can be dialed into the drug delivery device.
 9. The optical decoding system according to claim 1, wherein the processor is configured to determine a position of both the first and second movable components at the beginning and end of the medicament dose dispensing process based on the one or more images and to determine an amount of medicament dispensed based on the determined positions.
 10. The optical decoding system according to claim 1, wherein the first movable component comprises a hollow cylindrical number sleeve having numbers marked on a first portion of an outer surface and wherein encoded images are provided on a second portion of the outer surface.
 11. The optical decoding system according to claim 1, wherein the second movable component comprises a gear wheel having a plurality of teeth.
 12. The optical decoding system according to claim 11, wherein the encoded images are marked on crests of the plurality of teeth of the gear wheel.
 13. The optical decoding system according to claim 1 wherein the optical sensor is configured to be activated by movement of the first movable component.
 14. The optical decoding system according to claim 13, wherein the optical decoding system comprises a switch and wherein a change in a state of the switch is configured to cause the optical sensor to be activated.
 15. The optical decoding system according to claim 14, wherein the drug delivery device and the switch are configured to be arranged such that the state of the switch changes when the drug delivery device moves from a zero unit drug dose arrangement to a single unit drug dose arrangement.
 16. The optical decoding system according to claim 1, comprising a display device and wherein the processor is configured to cause the display device to display an indication of an amount of medicament that has been delivered.
 17. The optical decoding system according to claim 1, comprising one or more LEDs configured to illuminate portions of the first and/or the second movable components.
 18. The optical decoding system according to claim 1, wherein the optical decoding system is part of a supplementary device configured to be attached to the drug delivery device.
 19. The optical decoding system according to claim 1, wherein the optical decoding system comprises a switch configured to change between a first state and a second state upon movement of the first and/or the second movable components and wherein a change in state between the first state and the second state causes the optical sensor to be activated.
 20. A medicament delivery system comprising: a drug delivery device comprising first and second movable components each having a plurality of encoded images disposed around an outer surface thereof, wherein each of the encoded images corresponds to a discreet positions of respective first and second components; and an optical decoding system retained in a housing of the drug delivery device, the optical decoding system comprising: a single optical sensor configured to be directed at the first and second movable components; and a processor configured to: cause the single optical sensor to capture one or more images of the first and second movable components at least at a beginning and an end of a medicament dose dispensing process of the drug delivery device, determine a position of both the first and second movable components in each of the captured images.
 21. The medicament delivery system according to claim 20, wherein: the first movable component comprises a hollow cylindrical number sleeve having numbers marked on a first portion of an outer surface; the encoded images on the number sleeve are provided on a second potion of the outer surface; the second movable component comprises a gear wheel having a plurality of teeth; and the gear wheel is configured to be engaged with a drive sleeve of the drug delivery device during the medicament dose dispensing process. 